1. Technical Field
The present invention relates in general to diverter spools and, in particular, to an improved system, method, and apparatus for selectively opening and closing low pressure or uncontrolled outlets in two-stage diverter spools.
2. Description of the Related Art
Diverters are mounted to drilling rigs below the rig floor for use throughout the various stages of drilling. A support housing typically mounts below the rig floor and has a lateral flowline outlet for directing mud flow. The housing is a tubular member with an axial bore. A diverter body is secured to the upper end of a riser, is lowered through the rotary table, and lands in the housing. The diverter body has lateral flow openings that are axially aligned with the lateral flowline outlet. A pair of seals are usually located above and below the lateral flowline outlet.
The mud flow outlets are limited to low pressure or uncontrolled applications and are incapable of handling higher pressures associated with blow out preventers (BOPs). During standard operations, the mud flow is typically no more than a hydrostatic head pressure. When the BOP is located above the low pressure outlets, the diverter must be removed from the wellhead assembly prior to permitting high pressure flow through the assembly to the surface. Unfortunately, the down time and cost associated with the removal of the diverter can be significant. Thus, although prior art designs are workable, an improved design that overcomes the shortcomings of the prior art would be desirable.